CVC Preparation Flashcards
What is the convergence angle?
The angle or taper formed by diametrically opposed axial walls
What is retention form?
The characteristics of a tooth preparation that resist REMOVAL of a restoration along its POW
What is resistance form?
The characteristics of a tooth preparation that PREVENT DISLODGEMENT of a seated restoration by forces directed apical or oblique and prevents dislodgement by occlusal forces
What is the difference between resistance and retention form?
Resistance form: prevents dislodgment apical, oblique, occlusal
Retention form: resists removal along the POW
Which of the following is NOT an advantage of Complete Veneer Crowns?
- High Strength
- Longevity
- High resistance to displacement
- Margins close to gingiva
- Margins close to gingive = perio issues
The inability to test for ________ is a disadvantage of CVC preparation.
Pulp Vitality
Extensive destruction by caries, endodontically treated teeth, large existing restorations, and maximum retention needed are all ________ for CVC.
indications
True or False: Recontouring of axial surfaces and correcting malinclination are two indications for CVC.
True
What is a CONTRAindication for complete veneer crowns?
When a tooth can be restored with a more conservative restoration.
What are the three considerations/principles of tooth preparation?
- Biological: health of oral tissue
- Mechanical: integrity and durability of restoration
- Esthetic: appearance of the patient
________ form takes into account the magnitude and the direction of dislodging forces.
Resistance
To prevent deformation of the restoration, you need proper ______ selection, adequate tooth ________, and correct _______ design.
Alloy
Reduction
Margin
“A cast-gold extracoronal restoration which covers the clinical crown” is a definition of what type of crown?
CVC
“Extensive coronal destruction” would be a(n) ________ for a CVC.
indication
“An intact buccal or lingual wall” would be a(n) _________ for a CVC.
contraindication
“Maximum retention and resistance needed” would be a(n) ________ for CVC.
indication
“Endodontically treated tooth” would be a(n) ________ for a CVC.
indication
“Short clinical crown” would be a(n) ________ for a CVC.
indication
A complete cast crown allows the operator to modify _______ as well as ________.
Axial tooth contour
Occlusal discrepencies
What are the four disadvantages to using a CVC crown preparation?
- Removal of large amounts of tooth structure
- Adverse effect on tissue
- Display of metal
- Vitality testing not feasable
What is the “finish line”?
The terminal portion of the prepared tooth
What is a chamfer?
a finish line design for CVC tooth preparation in which the gingival aspect meets the external axial surface at an OBTUSE angle
What is “convergence angle”?
The taper of a crown preparation between opposing axial walls, measured in degrees
The long axis of the tooth is determined clinically by bisecting the angle between opposing axial surfaces in the _______ third of the tooth.
gingival
_______ is defined as the convergence of two opposing external walls of a tooth preparation. The extension of those planes will form the “angle of convergence”
Taper
*for CVC: there should be a 3 degree taper on each axial wall, resulting in an “angle of convergence” equal to 6 degrees
List the six steps in a CVC preparation:
- occlusal guide grooves
- occlusal reduction
- axial guide grooves
- buccal/lingual axial reduction
- interproximal axial reduction
- finishing and evaluating
What are the dimensions for proper CVC preparation? Central Groove Functional Cusp Non-functional Cusp Chamfer Width
- 0mm
- 5mm
- 0mm
- 5mm
Occlusal guide grooves should be placed with a _______ ________ bur in ______speed handpiece.
242.6 diamond
high
Depth grooves should be placed _____mm shallower than intended tooth reduction in order to allow for smoothing.
0.2mm
What is the width at the tip of the 242.6 diamond bur compared to the most proximal portion?
Distal (tip) = 0.8mm
Proximal = 1.3mm
Because the width of the proximal end of the 242.6 diamond bur is _______mm, the bur should only be buried completely on which part of the reduction?
1.3mm
Functional cusp and Functional cusp bevel
Occlusal guide grooves should be placed at the height of each _______ ridge, in the _______ and ______ grooves, and in the fossae grooves.
Triangular
buccal and lingual
The functional cusp bevel should be placed at what angle?
45 degrees to the long axis of the tooth
What is the purpose of the functional cusp bevel?
Ensures that correct contours of the final restoration can be re-established while providing adequate thickness of material on the functional cusp.
The final depth of the functional cusp bevel will be ______mm even though the initial guide grooves were placed ______mm deep to the unprepared surface.
- 8
1. 3 (buried the bur when placing functional cusp bevel grooves)
In order to check for “occlusal clearance” clinically, you will use a _________ gauge which has two ends measuring 1.0mm and 1.5mm.
Ball-Gauge
What does “conservation of tooth structure” mean for preparing a tooth for a CVC?
Minimum tooth reduction compatible with adequate strength and correct contours of the restoration
Moving a 242.6 diamond bur parallel to the long axis of the tooth will create a tapered surface that converges _____ degrees from the cervical toward the occlusal.
3 or 4 degrees
______ axial guide grooves should be placed in the buccal and lingual walls of the tooth.
Three
- center
- One at each mesial and distal line angle
The ______ of the diamond must be held parallel to the proposed path of withdrawal.
Shank
The chamfer should be _____mm wide and ____mm from the gingiva.
- 5
0. 5
Which part of the restoration is a potential site of failure due to cement dissolution or roughness?
The gingival margin
Axial walls should be extended interproximally until just short of _____ and then you should switch to a ___ _____ bur.
contact
169 L carbide
Interproximally, which three burs should be used?
169 L carbide
- 6M diamond
- 6M diamond
What three characteristics of preparation design would cause inadequate retention and resistance?
- excessive convergence angle (greater than 10 degrees)
- inadequate height of axial walls
- insufficient surface area to resist tipping
A wide margin, deviation from POW or tooth anatomy, and excessive convergence angle would result in _____.
Excess reduction ….less stability
True or False: A polished surface is unacceptable when preparing for a CVC.
True: there should be slight striations from the diamond burs
The final reduction at the central groove should be ____.
1.0mm
The final reduction on the functional cusp should be _____.
1.5mm
The interproximal chamfer should be placed with _____mm clearance.
0.5
The margin should be placed _____mm above the gingiva or _____mm coronal to the CEJ.
- 5
1. 0
Inadequate marginal integrity will occur if the chamfer is too _____ to provide correct amount of material or too _____ to allow proper adaptation.
narrow
rough
An undercut will cause distortion of the _____ pattern.
Wax
List the seven steps in a CVC preparation:
- occlusal guide grooves
- occlusal reduction
- Functional cusp bevel
- axial guide grooves
- buccal/lingual axial reduction
- interproximal axial reduction
- finishing and evaluating
What is a “long chamfer”?
One that starts too far coronal and then slopes down to the proper finish line (0.5 mm above gingiva).
The tips of the 242.6M and 747.6M diamond burs are ______ in order to produce a chamfer.
hemispherical
The path of withdrawal should be ______ degrees from the long axis.
+/- 5 degrees
The POW has a _____ inclination for mandibular molars.
lingual
Occlusal reduction should be done in a _____ orientation.
planar
Maxillary CVC preparations differ in that they require a ______ and a POW that is ______.
2nd plane reduction slightly buccal (functional cusp is lingual)
For maxillary CVC preparations there is a ______ second plane reduction that allows uniform reduction of 1.0mm.
Buccal
The buccal second plane of reduction for maxillary teeth should be placed according to what?
The previously unprepared angulation at the buccal surface.
*check angulation to adjacent teeth in the occlusal third of the buccal walls
The buccal first plane is from the gingival crest up to the junction of the ______ and _____ third of the tooth.
middle and occlusal
The buccal second plane of maxillary teeth is from the junction of the ______ and _____ third of the tooth up to the occlusal edge.
middle and occlusal
For maxillary CVC preparation, the lingual cusp reduction should be _____ and the linguo-occlusal line angle reduction should be ______.
- 5mm
0. 8mm
True or False: The second plane of reduction for maxillary CVC preparations should be carried interproximally.
False: taking the 2nd plane interproximally would overconverge the occlusal 1/3 of the mesial and distal axial walls.
Using a silicone mold, you should evaluate the ________ line angle of a mandibular preparation to determine the need for a non-functional cusp bevel.
linguo-occlusal
*Must be a MINIMUM of 0.6mm (ideal =0.8mm)
For a maxillary CVC preparation, the buccal second plane reduction should measure _____.
1.0mm
